struct Cat { meows : usize, how_hungry : isize, } impl Cat { pub fn eat(&self) { self.how_hungry -= 5; //~ ERROR cannot assign } } fn cat(in_x : usize, in_y : isize) -> Cat { Cat { meows: in_x, how_hungry: in_y } } fn main() { let nyan : Cat = cat(52, 99); nyan.eat(); }